Telecommunications transmission test set

ABSTRACT

A test set includes at least one signal input port, a test circuitry, a processor, a user-input device, and a display. The test circuitry couples to and receives signals from the at least one signal input port. The test circuitry then generates test data corresponding to the received signals. The processor couples to and receives test data from the test circuitry and generates test results. The processor also couples to and receives commands from the user-input device. The processor further operatively couples to the graphical display that receives and displays the test results from the processor. In one embodiment, the test set is capable of performing line qualification and connectivity testing. A modem module can be used to facilitate connectivity testing. The modem module can be a plug-in module with a common interface to the test set. The modem module can also contain a fingerprint value that identifies the module type and the software revision number to the test set.

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to test instrumentation, and inparticular to a telecommunications transmission test set for testingdigital communications networks.

[0002] The advent of digital communications networks, such as theInternet, has generated great demands for high-speed data services.Conventional telephone modems can provide a limited data rate (i.e., upto 56 Kbps) before reaching the limit of performance for thattechnology. Other technologies, such as cable modem, can offer a leapforward in performance but are typically premised on changes inarchitecture that requires large investments in the communicationsnetwork infrastructure.

[0003] Digital subscriber line (DSL) is a technology that offers asolution to the demand for greater bandwidth. DSL offers data rates thatcan be substantially higher than that of a conventional telephone modem.Furthermore, DSL uses existing twisted copper pair lines that aredeployed and prevalent throughout the world. DSL delivers a basic rateaccess of 128 Kbps (i.e., the ISDN rate). High speed digital subscriberline (HDSL), a variant of DSL, delivers a data rate of 1.544 Mbps (T1)in North America and 2.048 Mbps (E1) elsewhere. Asymmetric digitalsubscriber line (ADSL), another variant of DSL, delivers data rates of1.5 to 9.0 Mbps on the downstream path and 16 to 640 Kbps on theupstream path. More advanced variants of DSL promise even higher datarates. Collectively, DSL and variants of DSL are referred to as xDSL.

[0004] xDSL technology typically consists of a pair of modems connectedto two ends of one or more twisted wire pairs, depending on the xDSLvariant. One modem resides at a central office and the other modemresides at the customer premises. The twisted wire pair(s) forms a localloop. Generally, the maximum data rate is determined by the length ofthe local loop and the line conditions.

[0005] Installation, maintenance, and repair of an xDSL connectiontypically require execution of two sets of test: (1) line qualificationand (2) connectivity testing. Line qualification includes tests todetermine the quality of a line transmission that, in turn, determinesthe maximum data rate that can be achieved by an xDSL modem.Conventionally, a transmission impairment measurement set (TIMS) is usedto qualify a line for xDSL service. The TIMS measures impairments suchas frequency response, broadband noise, and signal power. One example ofa TIMS is the OneTouch Network Assistance from Fluke Corporation thatprovides testing of patch cable and fiber optic cable. Unfortunately,the OneTouch Network Assistance does not provide the traditional testsnormally required for line qualification and connectivity testing.

[0006] Once a line has been qualified and an xDSL modem has beeninstalled (i.e., at the central office), connectivity testing isperformed to verify data transmission over the modem. To performconnectivity testing, xDSL plug-in cards can be used. Generally, xDSL isprovided by a number of manufacturers, many with proprietary designs.Thus, an xDSL plug-in card of a particular manufacturer is installed inthe test equipment and connectivity tests (e.g., bit-error-rate (BER)and loopback tests) are then performed. This scheme presents a challengeto service technicians and telecommunications operators who need tomaintain an inventory of xDSL plug-in cards from various vendors. Inaddition, the technicians need to correctly select the appropriate xDSLplug-in card for the particular local loop being tested.

[0007] A number of other challenges arise in testing digitalcommunications networks. Conventionally, multiple types of testequipment are required to perform the various tests necessary to qualifya line and to test connectivity. For example, one type of test equipmentis used to qualify a line by performing various measurements (e.g., TDR,line impairment, and so on). Another type of test equipment is then usedto perform connectivity tests. The use of multiple types of testequipment increases the cost for installation, maintenance, or repair ofan xDSL connection since more equipment must be maintained. Furthermore,test setup and test time are increased.

[0008] To address the test needs of digital communications networks,some test equipment manufacturers integrate multiple tests into a singletest gear. One example of such integration is the CERJAC HDSLInstaller's Assistance from Hewlett-Packard Company. The CERJAC HDSLInstaller's Assistance performs line coil detection and insertion lossmeasurements (to qualify a line) and BER and transmission loopbacktesting (for connectivity testing).

[0009] Another challenge in testing digital communications networksarises because the line qualification and connectivity testing are oftenperformed in a mobile environment. The service technicians generallymove from site to site to test the local loop. Furthermore, access tothe local loop may be limited in certain instances. Conventional testequipment are generally bulky and cumbersome, and not well suited for amobile environment. For example, although touted as being portable, theCERJAC HDSL Installer's Assistance weighs a hefty 15 pounds.

[0010] Yet another challenge in testing arises because of the numerousamount of information that needs to be collected and presented foranalysis. During the testing process, measurements are made and the testresults are provided to a service technician who then configures thexDSL connection accordingly. In some conventional test sets, the testresults are conveyed through simple LEDs on the front panel. However,LEDs can only display a limited amount of information. For some tests(i.e., power spectral density and load coil detection tests to qualify aline), large amounts of information are generated. Conventionally, theinformation is displayed or printed using alphanumeric characters.However, an alphanumeric display can be difficult to decipher and proneto mistake in interpretation.

[0011] From the above, a telecommunications transmission test set thatis lightweight and portable, provides a comprehensive suite of tests,and intelligently displays test results is needed in the art.

SUMMARY OF THE INVENTION

[0012] The present invention provides a telecommunications transmissiontest set for testing digital communications networks In one embodiment,the test set is capable of performing line qualification testingincluding digital multimeter (DMM) tests, time domain reflection (TDR)test, and line impairment tests. The line impairment tests can includeinsertion loss, signal-to-noise, background noise, loop resistance, andother tests. In another embodiment, the test set is further capable ofperforming connectivity testing including loopback test and emulation.The test set can also be capable of performing bit-error-rate test(BERT). The test results can be graphically displayed on the test set.

[0013] In one embodiment of the invention, the test set includes a modemmodule that facilitates connectivity testing. The modem module can be aplug-in module with a common interface. This allows one test set to beused with various modem modules. The modem module can also include afingerprint value that identifies the modem module to the test set. Thefingerprint value can indicate the module type, the software revisionnumber, and so on. The test set then configures itself in accordancewith the fingerprint value from the modem module.

[0014] A specific embodiment of the invention provides a test set thatincludes at least one signal input port, test circuitry, a processor, auser input device, and a display. The test circuitry couples to andreceives signals from the at least one signal input port. The testcircuitry then generates test data corresponding to the receivedsignals. The processor couples to and receives test data from the testcircuitry and generates test results. The processor also couples to andreceives commands from the user-input device. The processor furtheroperatively couples to the display that receives and displays the testresults from the processor. In one embodiment, the test set is capableof performing line qualification and connectivity testing. The displaycan be a graphical display to show the test results in graphical forms.

[0015] Another specific embodiment of the invention provides a test setfor testing a communications network that includes a master tester unitand a modem module. The master tester unit receives a signal from thecommunications network and processes the signal to produce intermediateresults. The modem module couples to the master tester unit, receivesthe intermediate results, processes the intermediate results, andprovides processed results to the master tester unit. The master testerunit then displays the processed results. In a specific implementation,the modem module is a removable module (i.e., a plug-in module) thatsupports the test set in testing different communications networks(i.e., from different manufacturers). For example, a different modemmodule can be provided for each particular communications network to betested. The test set is configurable to perform line qualification andconnectivity testing.

[0016] The foregoing, together with other aspects of this invention,will become more apparent when referring to the following specification,claims, and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 shows a simplified block diagram of a digitalcommunications network;

[0018]FIG. 2 shows an embodiment of a telecommunications transmissiontest set of the invention;

[0019]FIG. 3A shows a block diagram of an embodiment of the test set;

[0020] FIGS. 3B-3D show block diagrams of an embodiment of a DMM testcircuit, a TDR test circuit, and a line impairment test circuit,respectively;

[0021]FIG. 4A shows a block diagram of an embodiment of the modemmodule;

[0022]FIG. 4B shows a diagram of an embodiment for identifying aparticular modem module to a test set;

[0023]FIG. 4C shows a diagram of another embodiment for matching theproper software application with a particular modem module;

[0024]FIG. 5 shows one embodiment of a menu tree;

[0025]FIG. 6A shows a test set up for DMM measurements;

[0026]FIG. 6B shows a graphical display of TDR test results, with“cursor” control;

[0027]FIG. 6C shows a graphical display of TDR test results, with“marker” control;

[0028]FIG. 7 shows a test set up for transmission line impairmenttesting;

[0029]FIG. 8A shows an embodiment of a menu for transmission lineimpairment testing;

[0030]FIG. 8B shows a menu that lists sets of test frequencies forinsertion loss measurement;

[0031]FIG. 8C shows a graph of an insertion loss test result;

[0032]FIG. 8D shows an alphanumeric display of insertion loss testresults;

[0033]FIG. 8E shows an alphanumeric display of a signal-to-noise testresult;

[0034]FIG. 8F shows a graphical display of background noise testresults;

[0035]FIG. 9A shows a test set up for dual HTU-C and HTU-R emulationover two wire pairs;

[0036]FIG. 9B shows a test set up for in-service HTU-C or HTU-Rfunction;

[0037]FIG. 9C shows a complementary test set up to that of FIG. 9B;

[0038]FIG. 9D shows a test set up for out-of-service HTU-C and HTU-Rfunction;

[0039]FIG. 9E shows a test set up for E1 and T1 testing on a HDSL span;

[0040]FIG. 9F shows a test set up for simultaneous ATU-C and ATU-Remulation;

[0041]FIG. 9G shows a test set up for testing ATU-C function; and

[0042]FIG. 9H shows a test set up for testing ATU-R function.

DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS

[0043] Network Configuration

[0044]FIG. 1 shows a simplified block diagram of a specific embodimentof a digital communications network 100. Network 100 includes a centraloffice 110 operatively coupled to a personal computer (PC) 120 throughxDSL modems 130 and 132. xDSL modem 130 couples to central office 110and to a splitter 140 a through a channel 142. xDSL modem 132 couples toPC 120 and to another splitter 140 b through a channel 144. Splitters140 a and 140 b are coupled through a local loop 150 composed of one ormore wire pairs, or other transmission media. Splitters 140 a and 140 balso couple to a public switched telephone network (PSTN) 152 and to atelephone 154, respectively, for providing a plain old telephone service(POTS). At the transmitting side, splitter 140 combines the POTS anddata service into a signal suitable for transmission over local loop150. At the receiving side, the other splitter 140 separates thereceived signal into the (lower frequency) voice telephone service andthe (higher frequency) data service. In this manner, both voice and datacan be transmitted over the same local loop concurrently without anymodification to that loop.

[0045] The test set of the invention can be used to test a wide varietyof communications networks, including network 100. As used herein,“communications network” generically (and broadly) refers to anystructure that supports a digital service carrier using any transmissiontechnology. The transmission technologies covered by the test set of theinvention includes plain old telephone system (POTS) modem, E1, T1,Integrated Services Digital Network (ISDN), Digital Subscriber Line(DSL), High data rate DSL (HDSL), Asynchronous DSL (ADSL), Very-highdata rate DSL (VDSL), Rate Adaptive DSL (RADSL), Single line DSL (SDSL),and other variants of DSL. DSL and variants of DSL are collectivelyreferred to as xDSL. The test set of the invention can also be adoptedto cover transmission technologies such as hybrid fiber coax (HFC),coaxial cable, optical fiber, and others. In a specific application, thetest set of the invention is especially suited for testingcommunications networks implemented using one or more twisted wirepairs.

[0046] Test Set

[0047]FIG. 2 shows an embodiment of a telecommunications transmissiontest set 200 of the invention. Test set 200 includes a light emittingdiode (LED) display 212, a graphical display 214, a keypad 216, and anintegrated microphone and speaker 218. LED display 212 indicatesoperational status of test set 200 as well as the operational mode andsignal/error conditions. Graphical display 214 displays the test menu,test parameters, and test results. Graphical display 214 can displayinformation in alphanumeric form, graphical form, or a combination ofboth. Graphical display 214 can be, for example a liquid crystal display(LCD). Graphical display 214 can also be substituted with analphanumeric display. Keypad 216 allows a user to select a test mode,specify the test conditions, control the test device, dial a phonenumber, manipulate a graphical display, scroll an alphanumeric display,and perform other functions.

[0048] Implementation of some of the features of test set 200 isdescribed in U.S. Pat. No. 5,619,489, entitled “HAND-HELDTELECOMMUNICATION TESTER,” issued Apr. 8, 1997, assigned to the assigneeof the present invention, and incorporated herein by reference.

[0049]FIG. 3A shows a block diagram of an embodiment of test set 200.Within test set 200, a processor 310 controls the operation of the testset according to program instructions stored in a memory 312. A digitalsignal processor (DSP) 314 can be used to assist in the processing ofdata samples (i.e., filtering, transformation, and so on). DSP 314 canbe implemented, for example, with a digital signal processor from theTMS320 line of processors from Texas Instruments, Inc. An expansion card316, which is an optional element, allows for easy upgrade to moreadvanced test features and more applications as they become available.Processor 310 couples to memory 312, DSP 314, and expansion card 316,and further to a bus 320 for communication with other circuits withintest set 200. DSP 314 can also couple to bus 320 to directly receivedata sent through the bus.

[0050] Processor 310 can be implemented with a microcomputer, amicroprocessor, a signal processor, an application specific integratedcircuit (ASIC), or the like. Memory 312 can be implemented as arandom-access memory (RAM), a read-only memory (ROM), a programmableread-only-memory (PROM), an electronically programmable read-only-memory(EPROM), a FLASH memory, registers, or other similar devices. Memory 312can be used to store the program codes or data, or both.

[0051] LED display 212, graphical display 214, and keypad 216 alsocouple to bus 320. LED display 212 and graphical display 214 receivecommands from processor 310 and provide the appropriate output on theirrespective displays. Keyboard 216 provides the user input to processor310.

[0052] A DMM test circuit 322, a TDR test circuit 324, and atransmission line impairment test circuit 326 couple to bus 320 and tothe network under test. Test circuits 322, 324, and 326 provide testsignals (e.g., test tones) and perform test measurements for variousline qualification tests that are discussed below. Test data generatedby the test circuits is provided via bus 320 to processor 310 thatfurther processes the data to generate the final test results which arethen displayed. The design for these test circuits are known in the artand are not described.

[0053] A modem module interface 328 couples to bus 320 and a modemmodule 330 via a module bus 332. Modem module 330 facilitatesconnectivity testing and is further described below. Modem moduleinterface 328 receives data and control signals from bus 320, formatsthe signals, and forwards the formatted signals to modem module 330.Modem module interface 328 also receives test data from modem module 330and forwards the data to processor 310. Modem module interface 328further acts as a conduit for the supply power to modem module 330.

[0054] Test set 200 also includes a power supply circuit 336 thatprovide power to the circuits within test set 200 and modem module 330.Power supply circuit 336 can receive power from a battery pack 362 or anexternal power supply source. Power supply circuit 336 can be aswitching power supply circuit, or other circuits. Power source 336 canalso include a charger, such as a battery charger, for charging batterypack 338 with the external power supply source.

[0055]FIG. 3B shows a block diagram of an embodiment of DMM test circuit322. In the embodiment shown in FIG. 3B, DMM test circuit 322 measuresthe line resistance, capacitance, DC voltage, and AC voltage. Initially,the line characteristics are converted into DC voltages by variousconversion circuits. An analog-to-digital converter (ADC) 340 thensamples the DC voltages on inputs 341 through 345 and provides thesampled values through bus 320 (i.e., to be received by processor 310and/or DSP 314). The samples are then processed to determine the linecharacteristics.

[0056] For line resistance measurement, a voltage divider 346 convertsthe line resistance into a DC voltage that is then provided to ADC input341. Voltage divider 346 couples to input 341, the line to be tested,and a test resistor 348 that further couples to a DC voltage source 350.In an embodiment, DC voltage source 350 provides eighty volts DC andtest resistor 348 is forty Kohms. For DC line voltage measurement, theline to be tested is directly coupled to ADC input 342. For AC linevoltage measurement, a root-mean-square (RMS) to DC voltage converter352 converts the AC voltage on the line into a DC voltage at input 343that is then sampled by ADC 340. And for line capacitance measurement,an AC voltage source 354 provides an AC voltage on the line under test.Two RMS to DC voltage converters 356 and 358 then convert the AC voltageon the line into DC voltages at inputs 344 and 345 that are then sampledby ADC 340. In an embodiment, AC voltage source 354 is a generator thatprovide a sinusoidal at 20 Hz and having 20 volts peak-to-peakamplitude.

[0057]FIG. 3C shows a block diagram of an embodiment of TDR test circuit324. A pulse generator 360 generates a pulse when directed by processor310. In an embodiment, pulse generator 360 has a variable time base andgenerates a single pulse when directed. A signal driver (AMP) 362, whichcouples to generator 360, receives and conditions the pulse and drivesthe line to be tested. The reflected pulse is provided to a signalreceiver 364 that conditions the received pulse. A programmable gainamplifier (PGA) 366, which couples to signal receiver 364, amplifies theconditioned pulse with a gain programmed by processor 310. A sample andhold analog-to-digital converter (ADC) 368, which couples to gainamplifier 366, samples the amplified pulse to generate sampled values. Alatch 370, which couples to ADC 368, latches the sampled values andprovides the latched values to bus 320. The pulse generated by generator360 is also provided to a programmable delay element 372 that delays thepulse by a programmed amount of time and provides the delayed pulse tobus 320. As shown in FIG. 3C, generator 360, delay element 372, latch370, ADC 368, and gain element 366 couple to bus 320 for receivingcommand from, and providing data to, other circuit elements that alsocouple to bus 320 (e.g., processor 310, DSP 314, and others).

[0058]FIG. 3D shows a block diagram of an embodiment of line impairmenttest circuit 326. A waveform synthesizer 380 generates a waveform (e.g.,sinusoidal, squarewave, sawtooth, or others) as directed by processor310. A lowpass filter 382, which couples to synthesizer 380, receivesand filters the generated waveform. A signal driver 384, which couplesto filter 382, receives and conditions the filtered signal and drivesthe line to be tested. The signal on the line is provided to a signalreceiver (AMP) 386 that conditions the received signal. A lowpass filter388, which couples to signal receiver 386, receives and filters theconditioned signal. An analog-to-digital converter (ADC) 390, whichcouples to filter 388, samples the filtered signal and provides thesampled values to bus 320. The sampled values are received and processedby, for example, processor 310 or DSP 314.

[0059] As shown in FIG. 2, test set 200 is designed to be a portableunit. In particular, test set 200 is dimensioned as a hand-held unit. Ina specific embodiment, test set 200 is implemented to weigh less thanthree pounds, thus improving its portability feature.

[0060] Modem Module

[0061]FIG. 4A shows a block diagram of an embodiment of modem module330. Modem module 330 emulates an actual xDSL modem (e.g., an Alcatelmodem, a Pair-Gain modem, or modems manufactured by other vendors) thatwill eventually be used (i.e., at the customer premises).

[0062] As shown in FIG. 4A, modem module 330 includes a processor 410that controls the operation of modem module 330 according to programinstructions stored in a memory 412. Processor 410 couples to modemmodule interface 328 of test set 200 via a data/address bus 420 and aserial bus 422. Through buses 420 and 422, processor 410 can send datato and receive instructions from test set 200. Processor 410 furthercouples to a modem circuit 430 and an optional test circuit 432.Processor 410 also optionally couples to a fingerprint circuit 434.

[0063] Processor 410 can be implemented with a microcomputer, amicroprocessor, a signal processor, an ASIC, or the like. Memory 412 canbe implemented as a RAM, a ROM, a PROM, an EPROM, a FLASH memory,registers, or other similar devices. Memory 412 can be used to store theprogram codes or data, or both.

[0064] Modem circuit 430 emulates the actual xDSL modem that willeventually be used for the communications network. Modem circuit 430generally includes circuits that generate, format, send, receive, andprocess test data. Circuits that perform at least some of thesefunctions are typically embodied in a chip set that can be obtained fromthe manufacturer of the actual xDSL modem. A processor within the chipset (not shown in FIG. 4A) typically controls the various functions.Modem circuit 430 can emulate a DSL, HDSL, ADSL, or other xDSL modems.Modem circuit 430 couples to a network interface 436 that provides aninterface to the communications network under test. Network interface436 can also provide circuit protection from transient signals on thenetwork, and other functions.

[0065] As shown in FIG. 4A, test circuit 432 couples to processor 410and modem circuit 430. Test circuit 432 can be used to provide variousfunctions such as, for example, to generate test patterns, to counterrors, to generate signals to control the modem, and to facilitate ATMSAR testing.

[0066] Modem module 330 also includes a fingerprint circuit 434 thatcontains a “fingerprint” value. The fingerprint value is anidentification value that identifies the a combination of: (1) the modemmodule type, (2) the software revision number, (3) the authorizationcodes, and so on, of the particular modem module 330. During aninitialization stage, the fingerprint value is provided to test set 200.A table within test set 200 contains a comprehensive list of possiblefingerprint values and their corresponding information. Test set 200then determines the identity of modem module 330 by matching thefingerprint value from module 330 with that from the table.

[0067] Test set 200 can then configure itself in accordance with thefingerprint value from module 330. For example, the module type (e.g.,Alcatel or PairGain) determines which connectivity test can beperformed. The software revision number determines the available testsand test configuration. The authorization code can be used to determinewhich tests are permissible for that modem module 330. For example, testset 200 can be designed and manufactured with the capability to performall tests. However, the authorization code of modem module 330determines which ones of the tests are available (i.e., based uponpayment of fees). Thereinafter, if the user selects a test not permittedfor that modem module 330, test set 200 can display a screen such as“Test Not Available.” In one embodiment, modem module 330 is implementedas a plug-in card that couples to test set 200. The use of plug-in cardis an improvement over conventional test sets that generally includebuilt-in circuits (i.e., fixed cards) within the test set. With the useof a plug-in card, the same test set 200 can be used to test variousxDSL modems by simply swapping plug-in cards.

[0068] Data/address bus 420 can be a universal data/address/control busthat is known in the art. Serial bus 422 can be a standard serial bus(i.e., an RS-232C bus having TTL logic levels). As shown in FIGS. 3 and4, power supply to modem module 330 is provided by test set 200. Thesevarious interface form a common interface scheme that allows test set200 to be coupled to various modem modules.

[0069] The common interface scheme also allows test set 200 to controlmost of the functions of modem circuit 430. For modem circuits thatinclude processors, communications between test set 200 and those modemcircuits can be direct. However, for modem circuits that do not includeprocessors, processor 410 provides the necessary interface between testset 200 and those modem circuits.

[0070]FIG. 4B shows a diagram of an embodiment for identifying aparticular modem module to a test set. In FIG. 4B, a common softwareapplication 452 is installed onto test set 450. For the required testing(i.e., of a particular modem manufactured by a particular vendor), oneof a set of modem modules 454 is coupled to (i.e., plugged in) a testset 450. Each of modem modules 454 includes an identification value(e.g., a fingerprint value) that identifies that modem module to testset 450. Test set 450 then executes the portion of the softwareapplication applicable for that particular modem module. For example,modem module 454 b can be plugged in, and the identification value frommodem module 454 b directs test set 450 to execute the “B” portion ofapplication 452 that is applicable to modem module 454 b.

[0071]FIG. 4C shows a diagram of another embodiment for matching theproper software application with a particular modem module. As shown inFIG. 4C, a test set 460 can be loaded with one of a number of softwareapplications 462 a through 462 n. Each software application 462 isdesigned for operation with a particular modem module 464. In thisembodiment, when a particular modem module 464 is plugged in, thecorresponding software application 462 is loaded onto test set 460 forexecution. As shown in FIG. 4C, modem module 464 a is plugged in testset 460 and corresponding software application 462 a is installed.

[0072] Menu Screen

[0073] Referring back to FIG. 2, a menu screen can be displayed ongraphical display 214 upon power up of test set 200. The menu screenallows the user to: (1) change test parameters; (2) select the test tobe performed; (3) store and recall test setup and/or resultsinformation; and so on. The user can navigate through the menu screenusing keypad 216.

[0074]FIG. 5 shows one embodiment of a menu tree. A main menu 510 can bedisplayed upon power up of test set 200 or by depressing a proper key onkeypad 216. As shown, main menu 510 includes the following choices: (1)xDSL, (2) DMM, (3) TDR, (4) Line, (6) Store/recall, and (6) other. Uponselecting the “xDSL” choice, a menu 512 is displayed. Menu 512 includesthe following choices: (1) HDSL and (2) ADSL. Upon selecting the “HDSL”or “ADSL” choice, a menu 514 or 516 lists the available setup and testoptions.

[0075] Similarly, upon selecting the “DMM” choice in main menu 510, amenu 518 lists the available tests. Upon selecting the “Line” choice, amenu 520 lists the available tests. And upon selecting the “Other”choice, a menu 522 lists the available configuration and setup choices.For each of the menus described above, additional or different choicescan be provided depending on the capability and design requirements oftest set 200.

[0076] Test Capabilities

[0077] In one embodiment, test set 200 is capable of performing bothline qualification and connectivity testing to allow completeinstallation, maintenance, and repairs of a xDSL connection. The testfeatures are described below.

[0078] Line Qualification Tests

[0079] Line qualification includes a variety of tests that measure thequality or transmission capability of a wire pair. These tests can begrouped into three categories: (1) digital multimeter (DMM), (2) timedomain reflection (TDR), and (3) transmission line impairments. DMMmeasurements can be used to detect shorts in the wire pair. TDR testscan be used to locate cable faults, such as the presence of loadingcoils, bridge taps, water, and so on. Transmission line impairment testscan be used to characterize the transmission capabilities of the lineand to determine if the wire pair is suitable for xDSL transmissionwithin a predetermined frequency range (e.g., 10 KHz to 1.5 MHz).

[0080] Digital Multimeter (DMM) Tests

[0081]FIG. 6A shows a test set up for DMM measurements. Test set 200couples to a wire pair 610 through a pair of clip cables 612. For a DMMmeasurement, a voltage is generated by test set 200 and provided acrosswire pair 610. Current is then detected from wire pair 610 to determinewhether a short (i.e., low impedance or high impedance short) exists inwire pair 610. The various DMM functions are known in the art and arenot discussed in detail in this specification.

[0082] In DMM mode, test set 200 can be used as a voltmeter or anohmmeter. As a voltmeter (for both DC and AC voltage measurements), testset 200 can detect and measure (foreign) voltages on a wire pair. As anohmmeter, test set 200 can be used to measure the resistance of a spanof a wire pair. Generally, the resistance of a span is greater than fiveMohm between a tip wire and ground and also between a ring wire andground. Test set 200 can also measure the capacitance of a wire pair,which is helpful to determine the length of a line.

[0083] Test set 200 can also be used to measure loop resistance betweena central office and the customer premises. The loop resistance is a DCmeasurement of the line. In one implementation of this test, two testsets are used, one located at the central office and the other at thecustomer premises. In an alternative implementation, one test set isused and the far end of the line is shorted. The loop resistancemeasurement can be used to verify that continuity exists between thecentral office and the customer premises and that no physical faults(e.g., grounds, shorts, or opens) exist in the loop.

[0084] For the various tests, the test result can be displayed ongraphical display 214. Generally, an alphanumeric display of themeasured voltage, resistance, or capacitance is adequate. The values canalso be automatically scaled (i.e., using nano, micro, milli, kilo,mega, or other suitable prefixes) and formatted.

[0085] Time Domain Reflectometer (TDR) Tests

[0086] TDR operates by sending a test pulse down a wire pair andmeasuring the reflections to determine “events” along the wire pair. Thereflections are influenced both by events that are normally expected(i.e., gauge changes and splices) and events that are undesirable (i.e.,water, shorts, and opens). The events identify changes in the impedanceof the wire pair, such as those caused by changes in: (1) insulationmaterial (e.g., water), (2) conducting material (e.g., corrosion), (3)capacitance (e.g., a split), and others.

[0087] For TDR tests, the configuration as shown in FIG. 6A is used.Test set 200 sends out pulses of energy, one pulse at a time. When areflection occurs, test set 200 measures the amplitude of the reflectedpulse and the time interval between the transmission of the pulse to thereception of the reflected pulse. The measured time interval is used todetermine the distance to the event. The amplitude of the reflectedpulse is then plotted against distance. A bump (i.e., upward deflectionfrom a baseline measurement) in the display indicates a high-impedanceevent. Alternatively, a dip (i.e., downward deflection from a baselinemeasurement) indicates a low-impedance event, such as a short. Based onthe graphical display, a user can determine a fault and the distance tothe fault.

[0088]FIG. 6B shows a graphical display of TDR test results, with“cursor” control. A result screen 630 can be reached from other menus oftest set 200 by depressing the proper key on keypad 216. A vertical axis632 represents the amplitude of the measured reflected pulse. Ahorizontal axis 634 represents distance. The vertical scale on axis 632can be adjusted by depressing the Up and Down arrow keys on keypad 216.Similarly, the horizontal scale on axis 634 can be adjusted bydepressing the F-keys on keypad 216. An output graph 636 represents themeasured results of the TDR measurement. Screen 630 also includes acursor 638 that can be moved left or right by the Right and Left arrowkeys on keypad 216.

[0089] An alphanumeric display section 640 lists pertinent dataassociated with the reflected pulse at the location of cursor 638. Thedata can include the amplitude of the reflected pulse, the distance tocursor 638, and so on. At the bottom of display section 640 are listeddisplay options that can be selected using the Function keys. Theoptions can include zoom in, zoom out, offset +, offset −, page left,page right, and so on.

[0090] In one embodiment, as cursor 638 is moved to a pulse, verticalaxis 632 is automatically adjusted (i.e., by adjusting the verticalgain, the vertical offset, or both) so that the pulse fits within screen630. The pulse can also be moved to the center of screen 630 bydepressing another key (not shown).

[0091]FIG. 6C shows a graphical display of TDR test results, with“marker” control. A result screen 650 is similar to result screen 630,but includes a marker 652 that can be selected with, for example, the F1key (see above discussion related to FIG. 6B). The marker can be movedleft or right by depressing the left or right arrow key on keypad 216.However, instead of listing the data at cursor 638 as with screen 630,display section 640 lists the difference between marker 652 and cursor638.

[0092] TDR can be used to locate various impairments in a wire pair thatare detrimental for high-speed data transmission. The impairmentsinclude load coils, split pairs, bridge taps, laterals, water,intermittent faults, and so on. A load coil is an inductive componentplaced on a telephone line to improve the frequency response over theaudio band (i.e., for voice communication). However, the load coilcauses a sharp roll off at high frequency and needs to be removed forhigh-speed digital data transmission. A split pair is caused when twotips of the same color, but from different pairs, are inadvertentlyspliced together. A bridge tap (i.e., similar to a splice) is interposedon a wire pair to allow attachment an additional circuit to the wirepair. A lateral is a portion of a cable pair that is not in the directpath between the central office and the customer.

[0093] TDR tests are further described in a product application noteentitled “Time Domain Reflectometry Theory” published by Hewlett-PackardCompany in May 1998. Methods for determining fault locations are furtherdescribed in a product application note entitled “Accurate TransmissionLine Fault Location Using Synchronous Sampling” published byHewlett-Packard Company in June 1998. Techniques for determining faultlocations are also described in a product application note entitled“Traveling Wave Fault in Power Transmission Systems” published byHewlett-Packard Company in February 1997. These application notes areincorporated herein by reference.

[0094] Transmission Line Impairment Tests

[0095]FIG. 7 shows a test set up for transmission line impairmenttesting. For this testing, two test sets 200 a and 200 b are used. Testsets 200 a and 200 b couple to wire pair 720 through respective pairs ofclip cable 722 and 724. Test sets 200 a and 200 b are configured in aparticular manner, depending on the test being conducted. Generally,master test set 200 a conducts the measurements and slave test set 200 bgenerates the required tones and properly terminates the far end of wirepair 720. Transmission impairment tests are further described in thepublication ANSI T1.413, which is incorporated herein by reference.

[0096]FIG. 8A shows an embodiment of a menu 810 for transmission lineimpairment testing. Menu 810 can be reached from other menus of test set200 by depressing the proper key on keyboard 216. Transmissionimpairment testing consists of the following measurements: (1) insertionloss, (2) signal-to-noise, (3) background noise, (4) loop resistance,and others. Also shown in menu 810 is a mode selection (i.e., master orslave) for the test unit.

[0097] Insertion Loss

[0098] Insertion loss measures signal attenuation versus frequencyacross the wire pair. For insertion loss measurement, slave test set 200b sends a tone from the far end of the wire pair. Master test set 200 athen measures the signal at the near end. Data is collected for a seriesof tone at various frequencies.

[0099]FIG. 8B shows a menu 820 that lists sets of test frequencies forinsertion loss measurement. For ADSL discrete multi-tone (DMT) test,measurements are collected for 256 frequencies. Other test frequenciesinclude: (1) 196 KHz for HDSL 2-pair T1, (2) 392 KHz for HDSL 1-pair T1,(3) 260 KHz for HDSL E1, (4) 40 KHz for ISDN U interface, (5) 96 KHz forISDN S interface, (6) 82 KHz for DDS, (7) 772 KHz for T1, and (8) 1.024MHz for E1. Alternatively, although not shown as a choice in FIG. 8B,the user can select a test frequency range and a frequency step size,thereby determining the frequencies to be tested.

[0100]FIG. 8C shows a graph of an insertion loss test result. A resultscreen 830 can be reached from other menus of test set 200 by depressingthe proper key on keyboard 216. A vertical axis 832 represents the valueof the insertion loss measurement. A horizontal axis 834 representsfrequency or the tones of interest. An output graph 836 represents themeasured result of the insertion loss measurement. A result can beplotted as each data point (or each frequency) is collected. A statusmessage 838 indicates the status of the test. For example, “Testing” canbe used to show that testing is in progress and “Complete” can be usedto show that testing is finished. A cursor 840 can be placed anywhere onoutput graph 836. An alphanumeric display section 842 lists pertinentdata associated with the test result at the location of cursor 840.Vertical axis 832, horizontal axis 834, and cursor 840 and be adjustedin similar manner to that described above for the TDR test.

[0101]FIG. 8D shows an alphanumeric display of insertion loss testresults. A result screen 850 lists the frequencies and the correspondingmeasured values. Screen 850 can be used to display a more preciselisting than output graph 836 shown in screen 830.

[0102] Although not shown, a setup screen can be created for the graphconfiguration and default values being used. The setup screen caninclude: (1) the unit being used (i.e., English or metric), (2) thegauge of the wire, (3) the propagation velocity, (4) the cable length,and other information.

[0103] Signal-to-Noise Ratio

[0104] Signal-to-noise ratio (SNR) measures the noise on a wire pairover a frequency band of interest. Referring to FIG. 7, forsignal-to-noise ratio measurement, slave test set 200 b sends a tonefrom the far end of wire pair 720. Master test set 200 a then performsmeasurements at the near end. The test result is then displayed. As withthe insertion loss measurement, various frequencies can be tested fordifferent operating modes.

[0105] In one embodiment, the SNR measurement is computed in accordancewith the following equation:

SNR=Signal (dBm/Hz)−Noise (dBm/Hz),  Eqn. (1)

[0106] where Signal and Noise are the signal and noise power,respectively, in units of dBm/Hz. In accordance with ANSI T1.413specification, equation 1 can be expressed as:

SNR=−40 dBm/Hz−Insertion Loss (dB)−Noise (dBm/Hz)  Eqn. (2)

[0107] where Insertion Loss is the insertion loss of the line undertest.

[0108]FIG. 8E shows an alphanumeric display of a signal-to-noise testresult. A result screen 860 lists the frequency under test and thesignal-to-noise ratio measurement result. Additional information (notshown) can also be displayed on screen 860, such as the center frequencyand the noise bandwidth, the start and stop frequency, the noise filterused, and so on.

[0109] Background Noise

[0110] Background noise measures the noise characteristics on the wirepair over a frequency band of interest. Referring back to FIG. 7, forbackground noise measurement, slave test set 200 b terminates the farend of wire pair 720 with the characteristic impedance of wire pair 720.Master test set 200 a then performs measurement of the extraneoussignals at the near end. A filter within test set 200 a can be used forimproved measurements. Example filters include: (1) an E-filter having a(−3 dB) passband of 1 KHz to 50 KHz (for ISDN BRA DSL) and acharacteristic impedance of 135 ohm, (2) an F-filter having a passbandof 5 KHz to 245 KHz (for HDSL) and a characteristic impedance of 135ohm, (3) an G-filter having a passband of 20 KHz to 1.1 MHz (for ADSL)and a characteristic impedance of 100 ohm, and other filters.

[0111]FIG. 8F shows a graphical display of background noise testresults. A result screen 870 includes a vertical axis 872, a horizontalaxis 874, an output graph 876, and a cursor 878. Screen 870 can alsoinclude a status message 880 indicating the status of the test. A resultcan be plotted as each data point (i.e., for a frequency) is collected.Cursor 878 can be placed anywhere on output graph 876. An alphanumericdisplay section 882 lists pertinent data associated with the test resultat the location of cursor 878. Vertical axis 872, horizontal axis 874,and cursor 878 and be adjusted in similar manner to that describedabove. The results shown in screen 870 can also be displayed on analphanumeric table, as described above. Furthermore, the backgroundnoise of the filters used in the testing can also be measured anddisplayed.

[0112] Loop Resistance

[0113] Loop resistance measures the impedance of a wire pair. Referringback to FIG. 7, for loop resistance measurement, slave test set 200 bshort circuits the far end of the wire pair. Master test set 200 a thenperforms measurements at the near end. The test result is thendisplayed.

[0114] Connectivity Testing

[0115] After a line has been qualified, connectivity testing istypically performed to verify proper operation of the actual xDSL modemcards to be used. Typically, a plug-in card that emulates the xDSL modemis installed on the test set. Then, a set of tests is performed tomeasure the quality of data transmission through the xDSL modem.Connectivity tests include: (1) HDSL transceiver unit remote terminalend (HTU-R) or HDSL transceiver unit central office end (HTU-C)function, (2) xDSL payload bit-error-rate test (BERT), (3) xDSL T1/E1framed BERT, (4) BERT using one of a set of predetermined pattern, (5)HTU-R and HTU-C loopback codes, (6) HTU-C line power generationimplemented by an external power supply, (7) HTU-R acceptance of linepower from HTU-C, and other tests.

[0116] The use of the plug-in card (or a “universal” plug-in) providesmany advantages. Generally, the modem interface is unique from one modemvendor to another. For example, Alcatel SA, Motorola Inc., PairgainTechnologies Inc., NEC Corporation, and Lucent Technologies Inc. areamong the vendors that use different modem chip sets having differentinterfaces. The plug-in card of the invention can be designed tointerface with these various modems, thereby allowing testing ofmultiple (seemingly incompatible) modems with one test set.

[0117] A network can be viewed as being composed of various layers, witheach layer performing a defined function. Each layer communicates withthe layer above or below it, or both. An Open System Interconnection(OSI) network is composed of seven layers including: (1) a physicallayer, (2) a data link layer, (3) a network layer, (4) a transportlayer, (5) a session layer, (6) a presentation layer, and (7) anapplication layer. The physical layer transmits bit streams across thephysical transmission system. The data link layer provides for areliable data transmission. The network layer routes data from onenetwork node to another. The transport layer provides data transferbetween two users at a predetermined level of quality. The session layermanages the data exchange. The presentation layer presents informationto the users in a meaningful manner. Finally, the application layermonitors and manages the computer network. The layers are furtherdescribed by G. Nunemacher in “LAN Primer”, M & T Books, pg. 179-181,which is incorporated herein by reference.

[0118] Layer 1 testing by test set 200 includes BERT, loopback controltest, and other tests. BERT includes tests using any permutation of thefollowing parameters: (1) T1 or El, (2) in HTU-C mode, in HTU-R mode,from Ti access point, or from El access point. Loopback control testincludes HTU-C, HTU-R, and CSU/NIU tests.

[0119] Layer 2 testing by test set 200 includes emulation, loopback, andother tests. For HDSL, HTU-R emulation, HTU-C emulation, HTU-R loopback,and HTU-C loopback can be performed. HTU-R loopback is a regenerativeloop back of the DSX-1 signal toward the network and HTU-C loopback is aregenerative loop back of the DS1 signal toward the network.

[0120] Layer 3 testing by test set 200 includes IP ping test and othertests. As an analogy, testing layer 2 and 3 is akin to testing amicrophone by saying “hello.” For this test, a source unit sends amessage to a far end unit that replies with a message back to the sourceunit.

[0121] The test set of the invention can be designed to test variousprotocols including ISDN, Asynchronous Transfer Mode (ATM), Frame Relay,and others. ATM interoperability testing is further described in aproduct literature entitled “Testing ATM Interoperability,” published byHewlett-Packard Company in June 1997, and incorporated herein byreference.

[0122] Emulation

[0123]FIG. 9A shows a test set up for dual HTU-C and HTU-R emulationover two wire pairs. Test set 200 a couples to one end of wire pairs 910a and 910 b. Test set 200 b couples to the other end of wire pairs 910 aand 910 b. The emulation test is used to verify that the wire pairs cansupport HDSL with an acceptable error rate.

[0124]FIG. 9B shows a test set up for in-service HTU-C or HTU-Rfunction. Test set 200 a couples to a T1/E1 connection 920 and to oneend of wire pairs 922 a and 922 b. The other end of wire pairs 922 a and922 b couples to an HTU-R 924 that further couples to a NIU 926 througha T1/E1 connection 928.

[0125]FIG. 9C shows a complementary test set up to that of FIG. 9B.HTU-C couples to a T1/E1 connection 932 and to one end of wire pairs 934a and 934 b. The other end of wire pairs 934 couples to test set 200 bthat further couples to a T1/E1 connection 936.

[0126] In the in-service HTU-C or HTU-R function mode, test set 200 canperform the following tests: (1) in-service BERT (east or west), (2)respond to loopback commands, (3) report modem status, (4) in-serviceHTU monitoring measurements, and others. In this mode, the test setsimulates a line terminating unit (LTU) or a networking terminating unit(NTU).

[0127]FIG. 9D shows a test set up for out-of-service HTU-C and HTU-Rfunction. Test set 200 couples to one end of wire pairs 942 a and 942 b.The other end of wire pairs 942 a and 942 b couples to an HTU-R or anHTU-C 944 that further couples to a NIU/CSU 946. NIU/CSU 946 isconfigured as a loopback.

[0128] In the out-of-service HTU-C and HTU-R function mode, test set 200can perform the following tests: (1) BERT at T1, (2) HTU/T1 loopback,(3) modem status, and others. These tests implement the HDSL loopbacktest.

[0129]FIG. 9E shows a test set up for E1 and T1 testing on a HDSL span.Test set 200 couples a HTU-C 950 through a T1/E1 connection 952. HTU-C950 couples to HTU-R 954 through wire pairs 956 a and 956 b. HTU-R 954couples to a CSU/NIU 958 through another T1/E1 connection 960. CSU/NIU958 is configured as a loopback.

[0130] In the E1 and T1 testing mode, test set 200 can perform thefollowing tests: (1) E1/T1 end-to-end BERT, (2) E1/T1/HTU loopbackcontrol, and others. These tests implement the TI loopback test.

[0131]FIG. 9F shows a test set up for simultaneous ATU-C and ATU-Remulation. Test set 200 a couples a splitter 970 a through a connection972. Splitter 970 a couples to another splitter 970 b though a wire pair974. Wire pair 974 is the connection being tested. Test set 200 bcouples to splitter 970 b through a connection 976.

[0132] In the simultaneous ATU-C and ATU-R emulation mode, test sets 200verifies that the wire pairs can carry ADSL with an acceptable errorrate.

[0133]FIG. 9G shows a test set up for testing ATU-C function. This testset up is similar to the configuration shown in FIG. 1, except that themodem at the customer premises is replaced by test set 200.

[0134]FIG. 9H shows a test set up for testing ATU-R function. This testset up is similar to the configuration shown in FIGS. 1 and 9G, exceptthat the modem at the central office is replaced by test set 200.

[0135] In the ATU-C and ATU-R function mode, test sets 200 verifies thatthe customer premise equipment is working properly.

[0136] The previous description of the preferred embodiments is providedto enable any person skilled in the art to make or use the presentinvention. The various modifications to these embodiments will bereadily apparent to those skilled in the art, and the generic principlesdefined herein may be applied to other embodiments without the use ofthe inventive faculty. For example, a test set can be designed with moreor fewer line qualification tests and more or fewer connectivity teststhan those disclosed. Furthermore, different graphical displays can begenerated for the test results. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein and as defined by the following claims.

What is claimed is:
 1. A test set for testing a communications networkcomprising: at least one signal input port; test circuitry coupled tothe at least one signal input port, the test circuitry receiving signalsfrom the signal input port and generating test data; a processor coupledto the test circuitry, the processor receiving test data and generatingtest results; a user input device coupled to the processor, the userinput device sending commands to the processor; and a displayoperatively coupled to the processor, the display receiving and showingthe test results, wherein the test set is capable of performing linequalification and connectivity testing.
 2. The test set of claim 1wherein line qualification includes transmission line tests, thetransmission line tests includes at least one of digital multimetertests, transmission impairment measurement set (TIMS) tests, and timedomain reflection (TDR) tests.
 3. The test set of claim 1 wherein thedisplay is a graphical display.
 4. The test set of claim 3 wherein thegraphical display shows selected ones of the test results in a graphicalform.
 5. The test set of claim 1 wherein the connectivity testingincludes bit-error-rate testing and loopback testing.
 6. The test set ofclaim 1 wherein connectivity testing is performed using a predeterminedtransmission technology.
 7. The test set of claim 6 wherein thepredetermined transmission technology is one of E1, T1, ISDN, DSL, HDSL,ADSL, and xDSL.
 8. The test set of claim 1 wherein the test set isbattery powered.
 9. The test set of claim 1 wherein the test set is aportable unit.
 10. The test set of claim 1 wherein the test set is ahand held unit.
 11. The test set of claim 1 wherein the test set weighsless than three pounds.
 12. The test set of claim 1 further comprising:a modem module operatively coupled to the processor, the modem modulereceiving and processing the test data and generating processed results,and wherein the display receives and displays the processed results. 13.The test set of claim 12 wherein the modem module includes a device forstoring an identification value that identifies the modem module to thetest set.
 14. The test set of claim 12 wherein the modem module isconfigured to perform xDSL connectivity testing.
 15. The test set ofclaim 12 wherein the modem module is configured to perform ATMconnectivity testing.
 16. A telecommunications transmission test setcomprising: at least one signal input port; test circuitry coupled tothe at least one signal input port, the test circuitry receiving signalsfrom the signal input port and generating test data; a processor coupledto the test circuitry, the processor receiving test data and generatingtest results; a modem module operatively coupled to the processor,wherein the modem module, when directed, receives and processes the testdata to generate processed results, and wherein the processor generatesthe test results based, in part, on the processed results; a user inputdevice coupled to the processor, the user input device sending commandsto the processor; and a display coupled to the processor, the displayreceiving and displaying the test results, wherein the test set isconfigurable to perform line qualification or connectivity testing asselected by a command received from the user input device.
 17. The testset of claim 16 wherein line qualification includes digital multimetertests, time domain reflection tests, and transmission line impairmenttests.
 18. The test set of claim 16 wherein connectivity testingincludes bit-error-rate testing and loopback testing.
 19. The test setof claim 16 wherein connectivity testing can be performed using apredetermined transmission technology.
 20. The test set of claim 16wherein the test set is a portable unit.
 21. The test set of claim 16wherein the test set is a hand held unit.
 22. A test set for testing acommunications network comprising: a master tester unit for receiving asignal from the communications network and processing the signal toproduce intermediate results; and a modem module coupled to the mastertester unit, wherein the modem module receives and processes theintermediate results and provides the processed results to the mastertester unit, wherein the test set is configurable to perform linequalification and connectivity testing, and wherein the master testerunit displays the processed results.
 23. The test set of claim 22wherein the master tester unit includes a graphical display for showingthe test results in graphical form.
 24. The test set of claim 22 whereinthe modem module includes a memory for storing an identification valuethat identifies the modem module to the master tester unit.
 25. The testset of claim 22 wherein the modem module determines a maximumtransmission rate on the communications network based on the processedresults.
 26. A hand-held device for testing communications networkscomprising: at least one signal input port; test circuitry coupled tothe at least one signal input port, the test circuitry receiving signalsfrom the signal input port and generating test data; a processor coupledto the test circuitry, the processor receiving test data and generatingtest results; a user input device coupled to the processor, the userinput device sending commands to the processor; and a display coupled tothe processor, the display receiving and displaying the test results.27. A method for graphically displaying test results of a test of adigital communications network comprising the steps of: receivingsignals from at least one signal input port, the signals beingresponsive to the test being conducted; processing the signals togenerate test results; and displaying the test results in graphicalform, wherein the test can be one of line qualification or connectivitytest of the digital communications network.